As a method of collecting and removing the particulate matter from the gas, an electric dust collecting apparatus is well known. The dust collecting apparatus collects the particulate matter charged by corona discharge occurring in the gas onto a dust collection electrode installed in the gas by the Coulomb's force.
Since particles having a large particle diameter have a large charge amount, those particles can be easily collected on the dust collection electrode by the Coulomb's force. However, particles having a small particle diameter are hard to be charged, and hence the Coulomb's force acting thereon is also weak. Furthermore, the particles having a small particle diameter have essentially a property such that the behavior thereof is governed by air flow (particles moves together with the air flow along the stream line of the air flow), and hence, collection thereof by the electric dust collecting apparatus is difficult.
In order to compensate for the above defect, and improve the particle collection characteristics by using the fact that the behavior of particles having a small particle diameter is governed by the air flow, there is a dust collecting apparatus (dust remover) applying the corona discharge. The dust remover includes a discharge electrode provided in the gas flow containing particulate matter, and a counter electrode (ground electrode) arranged opposite to the discharge electrode, wherein a high voltage is applied to between the discharge electrode and the counter electrode. For example, Japanese Patent Application Laid-Open No. H2-63560 (Page 2, left-lower column line 6 to page 3, right-upper column line 19, and FIGS. 1 to 3) describes one in which a wire mesh (mesh) is used as the counter electrode, and a dust removal filter is provided at the opposite side of the discharge electrode, with the counter electrode being put therebetween.
The particulate matter in the gas having flown along the discharge electrode deflects toward the counter electrode due to the Coulomb's force, as a result of being charged. The gas having flown along the discharge electrode is turned in the cross section of the flow path along the gas flow, due to the ion wind generated by a high voltage applied to between the discharge electrode and the counter electrode, and deflects toward the counter electrode. By adjusting a bleeder that adjusts the gas flow rate passing through the dust removal filter and allowing the gas in which the particulate matter deflects to pass through the dust removal filter, dust removal is realized.
Furthermore, for example, Japanese Patent Application Laid-Open No. H2-184357 (Page 3, right-upper column line 19 to page 4, right-upper column line 15, and FIGS. 1 to 6) describes a dust collecting apparatus in which a closed space is provided on the side opposite to the discharge electrode with respect to a filter formed of a counter electrode (ground electrode) and a dust removal filter. The dust collecting apparatus charges the particulate matter in the main gas having flown along the discharge electrode. As a result, the particulate matter deflects toward the counter electrode due to the Coulomb's force. The gas having flown along the discharge electrode flows into the filter in the cross section in the longitudinal direction along the gas flow (main gas flow) due to the ion wind, and is accumulated in the filter and the closed space for some time. The particulate matter in the gas is filtered while the gas is accumulated in the filter and the closed space. In this dust collecting apparatus, since the gas in the closed space is replaced by the gas newly flowing into the filter from the flow path where the gas flows, a bleeder is not required.
For example, Japanese Patent Application National Publication No. 2003-509615 (Paragraphs [00191]to [00291]and FIG. 1) describes a processor having an electric filter and a plurality of serrated plates arranged in a direction transverse to a gas passage, wherein the respective tips of the serrated plates are directed toward a collector (filter) provided along the inner face of a housing. The serrated plates are formed of a star-shaped member, and generate not only corona discharge but also local turbulence. Accordingly, fine particles are accelerated toward the collector in the longitudinal direction (in the direction along the main gas flow).